1. Field of the Invention
The present invention relates to a softener, and more particularly it relates to a softener which imparts improved softness, antistatic property, and water absorbency to a variety of fibers.
2. Description of the Prior Art
Clothes often exhibit poor handleability after repeated wearing and washing because the fiber loses the finishing agent and gets harsh due to the deterioration of fiber itself. For this reason, softeners have come into common use in the home in order to impart softness and antistatic property to fibers.
The commercial softeners for household use are mostly ones which are composed mainly of a cationic surfactant having one or two long-chain alkyl groups in one molecule, particularly one which is composed mainly of di(hydrogenated tallow alkyl)dimethylammonium salt.
This quaternary ammonium salt, even in a small quantity, imparts good softness and antistatic property to a variety of fibers. It produces the softening effect because the lipophilic moiety of the molecule adsorbed to the fiber surface produces the lubricating effect, reducing the coefficient of friction of the fiber surface. Therefore, it is considered that the lipophilic property is indispensable for the good softening effect. On the other hand, the lipophilic property has a shortcoming of making treated clothes water-repellent and lowering the water absorbency of treated clothes. Decrease in water abosorbency is remarkable especially in the case where the concentration of softener is high.
Consequently, studies have been made on the improvement of water absorbency, and some compounds have been found effective. They include a branched alkyl quaternary ammonium salt [as disclosed in U.S. Pat. Nos. 3,377,382 and 3,395,100] and an imidazolium compound derived from oleic acid [as reported in Journal of American Oil Chemical Society (JAOCS), 61, 367 (1984)]. These compounds are certainly effective in the improvement of water absorbency; however, on the other hand, they are poor in softening effect and are apparently inferior to the above-mentioned di(hydrogenated tallow alkyl)dimethyl quaternary ammonium salt. For the reinforcement of softening effect, the imidazolium compound is usually used in combination with distearyldimethylammonium chloride or an imidazolium compound derived from hydrogenated tallow fatty acid. The combined use, however, does not provide satisfactory water absorbency. In the case of .alpha.- or .beta.-branched alkyl quaternary ammonium salt, the problem is solved by the combined use with a linear alkyl quaternary ammonium salt (see Japanese patent application Laid-open Nos. 69998/1974, 53694/1975, 122207/1979, and 144174/1983; U.S. Pat. No. 3,892,669; and West Germany Pat. No. 2625945). None of the above-mentioned prior art, however, provide satisfactory softening effect.